A laundry treating appliance is a common household device for treating laundry in accordance with a preprogrammed treating cycle of operation. The laundry treating appliances typically have a configuration of a rotating drum positioned within a tub. The rotating drum is typically perforated and at least partially defines a treating chamber in which a laundry load is received for treatment according to the cycle of operation. The tub is typically imperforate and retains liquid used to treat the laundry load. A lower portion of the tub is typically used as a sump to collect the liquid.
The volume of liquid used in a laundry treating appliance may vary with fabric type, load size, and cycle of operation. Therefore, a liquid fill control is used to provide for the desired amount of the liquid. Known liquid fill controls include a pressure sensor to provide feedback for controlling the filling process. The pressure sensor may be coupled with a pressure tube fluidly coupled with the sump. As the machine fills, pressure inside the tube increases in direct proportion to the height of the liquid in the sump.
The pressure in the pressure tube is sensed by the pressure sensor, and is a function of the volume of free liquid in the sump, i.e. liquid not absorbed by and retained by the laundry load, and the angle of the tub and sump. When the washer fills with liquid, this angle may change depending on various factors such as how the laundry was loaded in the treating chamber and how the tub is suspended relative to the loading.
Loading of a front-loading laundry treating appliance, or “front loader,” with laundry may result in an accumulation of laundry toward the forward end of the drum. These machines also typically fill from the forward end of the wash tub. Laundry in the forward portion of the drum may, therefore, be wetted first. This may increase the weight of the laundry load, particularly if the fabric comprising the load is relatively absorbent, and the forward portion of the tub may tilt downward in response. This tilting changes the angle of the tub and sump, and the angle of the free-liquid surface in the sump, which is sensed by the pressure sensor as a decrease in volume of the liquid, which results in an error in the reading of the pressure sensor.
The amount of error is, to some extent, a function of the relative locations of the load and pressure sensor as well as the type of suspension. The error may be on a single axis or multiple geometric axes of the tub. For example, in front loading laundry treating appliances, the pressure sensor is at the rear of the tub, opposite where the laundry is loaded, leading to a front-to-back error. The pressure sensor may also be laterally offset from the load, leading to a side-to-side error.
The erroneous reading will lead to either too much or too little liquid being supplied to the tub for the selected treating cycle of operation, which is undesirable in that it may lead to improper treating, increased energy costs, particularly if heated liquid is utilized and increased costs of water as a result of the excess.